Abstract
Very little is known about the in vivo toxicity of inhaled double-walled carbon nanotubes (DWCNTs). In the present study, we compared the pulmonary toxicity of DWCNT to MWCNT-7, a well-known multi-walled carbon nanotube. Rats were divided into six groups: untreated, vehicle, low-dose DWCNT, high-dose DWCNT, low-dose MWCNT-7, and high-dose MWCNT-7. The test materials were administered by intra-tracheal intra-pulmonary spraying (TIPS) every other day for 15 days: the low-dose and high-dose groups were administered final total doses of 0.25 and 0.50 mg/rat of the test material. The animals were sacrificed 1 and 6 weeks after the final TIPS administration. Six weeks after the final TIPS administration, rats administered MWCNT-7 had high levels of macrophage infiltration into the lung with dense alveolar wall fibrous thickening throughout the lung; significant elevation of lactate dehydrogenase activity, alkaline phosphatase activity, and total protein concentration in the bronchioalveolar lavage fluid; an increase in the pulmonary cell PCNA index; slightly elevated levels of 8-OHdG DNA adducts in lung tissue DNA; a small but significant increase in protein concentration in the pleural cavity lavage fluid and an increase in the visceral mesothelial cell PCNA index. None of these parameters was increased in rats administered DWCNT. The primary lesion in rats administered DWCNT was scattered formation of granulation tissue containing internalized DWCNT fibers. Our data indicate that DWCNT has lower pulmonary and pleural toxicity than MWCNT-7.
Highlights
Carbon nanotubes (CNTs) are composed of one or more oneatom thick graphene cylinders
A second study reported that intratracheal instillation of 50 μg double-walled carbon nanotubes (DWCNTs) to mice caused pulmonary inflammation that persisted for 7 days (Tian et al 2013)
A third study reported that 56 days after pharyngeal aspiration of 40 μg DWCNT to mice, DWCNT induced a greater degree of alveolitis and lung fibrosis than a administered MWCNT (Sager et al 2013)
Summary
Carbon nanotubes (CNTs) are composed of one or more oneatom thick graphene cylinders. Archives of Toxicology (2019) 93:49–59 mechanical, thermal, chemical, and electrical properties, and their hollow tubular structure makes them very light weight These properties make CNTs airborne and highly biopersistent in tissues when inhaled. Rats administered MWCNT-7 had extensive inflammatory lesions, increases in tissue damage parameters in the lung and pleura, increases in the PCNA indices in the lung and pleura, and increased 8-OHdG levels in lung tissue DNA. Overall, these preliminary results suggest that the DWCNT we are examining is less toxic than MWCNT-7. Our ongoing 2-year study will resolve the toxicity of this DWCNT in the rat lung and determine the relevance of the findings reported here to its long-term toxicity
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